The invention relates to an automatic sequencing valve which hydraulically lowers and raises a pair of row marker arms on a conventional row planter.
Most crops today are planted by large tractor-pulled planters which seed many rows on a single pass. On the return pass through the field, the farmer needs a reference line to steer to so that all the rows will be equally spaced across the field. Since the already planted rows are not easily distinquishable in the field, it has become necessary to establish some form of reference mark in the field away from the planted rows which the farmer can follow as he seeds the adjacent returning row.
The use of retractable row markers have long been in use and basically entail a pair of pivoting arms which have a small disc or other ground marking device on the end thereof for marking a reference line as a row is planted. At the end of the field, the farmer will lift his planter out of the ground to stop the seeding until the tractor and planter can be circled around for a return pass at which time the planter is again lowered into the ground. There have been a variety of mechanical and hydraulic methods for alternately raising and lowering the marker arms as the operator reverses direction at the end of the field; some of which have been manual while others have been automatic. The automatic systems for the most part have been tied to the planter lift cylinder so that as the lift cylinder raises the planter out of the ground, one or both of the marker arms are elevated, and as the planter is again lowered on the return pass, the opposite marker arm from the one previously lowered is dropped. Some of these automatic systems have been completely mechanical in nature, such as shown in U.S. Pat. Nos. 3,454,103 and 3,428,134. Automatic systems which utilize hydraulic cylinders for raising and lowering the marker arms in conjunction with the lift cylinder on the planter controlled by an automatic sequencing valve are typified in U.S. Pat. No. 4,067,394 to Deckler. In the last-mentioned patent the automatic sequencing valve is actuated by differing pressure drops across a valve spool.